Improvement in iron viaducts



UNITED STATES PATENT OEEIoE.

O. SHALER SMITH, OF BALTIMORE, MARYLAND, ASSIGNOR TO THE BALTIMOREBRIDGE COMPANY, OF SAME PLAGE.

IMPROVEMENT IN IRON VIADUCTS.

Specification forming part of Letters Patent No. lll ,010, dated`Ianuary 17, 1871.

To whom it may concern:

Be it known that I, C. SHALEE SMITH, of the city and county ofBaltimore, and State of Maryland, have invented certain new and usefulImprovements in Bridges, of which the following is a specification:

My invention relates to trestle bridges or viaducts, and its object isto make such structures entirely of iron.4

In Letters Patent No. 97,975, granted to Smith, Latrobe & Smith on the14th December, 1869, is described a bridge composed of continuoustrestle; and in order to avoid the injurious effects consequent upon theexpansion or contraction of metal-top members and the system oflongitudinal struts, both the chord-sticks and the struts are made ofwood.

It is my desire to avoid the use of wood and to make the bridge orviaduct all iron; and to this end I make the trestle entirely of iron,and provide for expansion and contraction byy leaving out thelongitudinal braces and struts in certain panels of the structure, andby making the truss spanning these panels with an expansion-joint-thatis to say, the truss has one or both of its ends loose, so as to permitof expansion or contraction of any one part of the bridge withoutderanging the rest of the trestle.

The bridge is thus made up of fixed piers composed of any number ofpanels of trestle alternating with spans of truss, 'having one or bothends loose, so as to permit of contraction or expansion. By this means Ican make all parts of the structure of iron, rendering it unnecessary touse wood, and producing a strong and very durable viaduct.

The manner in which my invention is or may be carried into effect willbe understood by reference to the accompanying drawing, in which- Figurel is an elevation of a bridge made in accordance with my invention. Fig.2 is a like view, on an enlarged scale, of the joint between the fastand loose spans.

The general arrangement of the bridge requires but little explanation.

The tresth'ng is shown at A, the fixed spans or top members at B, andthe loose spans at C.

The system of bracing represented in the drawing is that employed in thebridge described in the said Letters Patent, and c c are thelongitudinal struts, which, in the continuous trestle heretoforeemployed, have been made of wood.

It will be observed, however, that in the present structure the trestleis not continuous; but the braces and struts have been removed atintervals from some of the panels or bents, leaving a series of pierscomposed of one or more panels of trestle'and connected by spans oftruss of greater or lesser length, according l to the distanceintervening between the piers. The chords b b are made also of metal,both in the fast and the loose spans, as shown more resented as restingon rollers c on the top of y the cap of one of the columns making partof the pier. p

The expansion panels and spans may be at regular or irregular'intervals, alternating with one or more panels of fixed trestle.

Having now described my invention, and the manner in which the same isor may be carried into eiiect, what I claim, and desire to secure byLetters Patent, is

An all-iron trestle formed of fixed piers com= posed of any number ofpanels of trestle, as described, alternating with spans of truss, eachhaving one or both ends loose to permit of expansion and contraction,substantially as and for the purpose set forth.

In testimony whereof I have signed myname to this speciiication beforetwo subscribing witnesses.

C. SHALER SM ITI-I Witnesses:

Jos. H. ALEXANDER,- HENRY B. DENKER

